Questions on computers

[tstormdiver]

Perhaps this has been discussed before- If so I'm sorry. I am still very new to diving (less than a year) and do not yet have my own computer. After purchasing all the basic equipment I need, it will be some time before I can afford a computer of my own (hopefully early next year, until then I'm stuck with the tables). Any way , Later this summer I will be going on a live aboard cruise in the Bahamas. I have arrainged to rent a computer from the company offering the cruise, since I am planning on doing multiple dives over multiple days. I am hoping that my LDS will be holding a Multi level & Computer diving specialty class before I leave on this trip (I have talked to my instructor & she said that they probably will have a class), but if not I am curious to know how do you work one? Figure out you dive profile for the log book? I am going to definately take some extra batteries for the computer and use my gauges for a back- up. I am not looking for an online class on the subject, just some basic ideas that will make my diving trip more enjoyable. Any thoughts or suggestions would be greatly appreciated.

 

[H2Andy]

first, you will need to read the computer manual. that's where the information is,
and it will vary from model to model.

but basically, the computer will display:

your current depth
your deepest depth so far
minutes left of no-deco-time at this depth
total minutes in the dive so far

(other models display other information, such as time, temperature, etc.)

you don't really need a class to dive with a computer; simply read the
manual, and understand the information the computer will be giving you.

can you get an experienced friend to lend you his or her computer and
go diving with you ahead of time?

in planning mode, before a dive, your computer will tell you how long
you have at the various depths. for example, it'll tell you you have
40 minutes at 70 feet. note that, and keep an eye out so that you
do not exceed that time.

in planning mode (between dives) the computer will indicate what your
maximum NDL's will be at various depths. as your interval goes on,
these figures will continue to increase. this will help you plan your next
dive (for example, if your max NDL at 40 feet is 120 minutes, you know
that you can do a really long dive and will have to call the dive on
gas, not time; if, on the other hand, your NDL at 40 feet is only 20
minutes, you need to keep an eye on that time so it doesn't creep
up on you)

 

[tstormdiver]

Yes, I agree, definately read the manual. I am hoping I can get with some local people here that may have an extra computer. I'll also be asking lots of questions about the operation of theirs if they don't have an extra. The planning mode you spoke of looks like it could be a good tool. Before I leave I will definately try to get as much information & experience with one as I can. Who Knows I might even be able to somehow scrape up enough $ to get at least a basic model.

 

[Matsya]

H2Andy has covered most of it.


It would also help, I think, if the computer you are renting:

1. Is new or unused, or
2. Has had previous dive histories/logs/memory deleted from it.
3. Or, as a last preference, has not been used in the last 48 hours.

The above is because the computer stores info from previous dives to keep track of NDL/Deco, Surface Interval etc. and if you dive with one that has been used recently it could give you wrong/lesser NDLs, no fly times etc.

Am I right folks?

 

[H2Andy]

oh very good point that the computer should be "clean"

it someone just dove with it, the computer will treat your first dive as a "repeat"
dive and will penalize you for it.

 

[tstormdiver]

I see, good thoughts. The computer I rent (I will assume) to be used. I will see to it that past records are deleted. Like I said also, I may look into getting my own computer & forgo the rented one. I'll have to take a close look at what finances will allow. I'm getting a lot of good info, thank you very much.

 

[Damselfish]

I wouldn't worry about taking extra batteries for a rental computer, batteries last pretty long and this should not be your responsibility for a rental computer - in fact you would not want to risk changing the battery improperly in a rental and having it flood. Nor do you want to change the batteries in the middle of the week if it's a computer that will forget everything during the change. Many computers have some kind of battery life remaining indicator and it's definitely worth checking that when you first get the rental.

I certainly wouldn't expect a rental computer to be new as someone suggested, what are they going to do rent it once and throw it away? It doesn't really matter if there are old dives in the built in log either, as long as the computer is still not counting down from the last dives someone did with it. This is something you or the shop should make sure of but on a liveaboard probably any rentals they have would be long cleared by the time you get it and start diving - all the customers from the previous trip would have finished up diving around the same time and waited long enough to fly by then. There may be some computers used more for rentals because they have an easy ability to clear everything, but some don't have a way to do that. Don't worry about it too much.

As far as logging dives, the standard time and depth entries in typical logbooks are intended more for when you are diving tables. These are good to track of course but not quite as useful when you're diving a computer. Your computer will be happy while the tables would likely be declaring you dead. It's impractical to write down everything the computer tracks, just write down max depth and time and maybe average depth if it shows that, but don't get overly hung up on it.

Getting your own computer would be good because you would be familiar with it. A basic Nitrox computer is not that expensive and would pay for itself after a few trips. Unless you get some really good used deal, definitely buy a Nitrox computer even if you're not diving Nitrox now, sooner or later you will probably want the capability. In fact, liveaboards are a great place to use Nitrox and some offer really good deals for the class + Nitrox for the trip.

 

[tstormdiver]

Good thougts Damselfish. Everyone has given me very useful information. I like knowing what pitfalls and positives to look for when engaged in in a new activity

 

[--tom--]

If you are fortunate enough to know the make and model of the computer you are renting, many of the computers have their manuals online. I know Suunto does.

 

[Sting J]

Aeris and Oceanic have manuals online as well. You definately want to make sure the computer has not been dove for 24 hours, or have the memory cleared, which depends on the model on how to do that. Ramsabi had a very good point there. The shop renting the computers should have some routine for doing just that but final safety checks like that double check yourself